The Integrin Antagonist Cilengitide Activates αVβ3, Disrupts VE-Cadherin Localization at Cell Junctions and Enhances Permeability in Endothelial Cells

Cilengitide is a high-affinity cyclic pentapeptdic alpha V integrin antagonist previously reported to suppress angiogenesis by inducing anoikis of endothelial cells adhering through alpha V beta 3/alpha V beta 5 integrins. Angiogenic endothelial cells express multiple integrins, in particular those of the beta 1 family, and little is known on the effect of cilengitide on endothelial cells expressing alpha V beta 3 but adhering through beta 1 integrins. Through morphological, biochemical, pharmacological and functional approaches we investigated the effect of cilengitide on alpha V beta 3-expressing human umbilical vein endothelial cells (HUVEC) cultured on the beta 1 ligands fibronectin and collagen I. We show that cilengitide activated cell surface alpha V beta 3, stimulated phosphorylation of FAK (Y(397) and Y(576/577)), Src (S(418)) and VE-cadherin (Y(658) and Y(731)), redistributed alpha V beta 3 at the cell periphery, caused disappearance of VE-cadherin from cellular junctions, increased the permeability of HUVEC monolayers and detached HUVEC adhering on low-density beta 1 integrin ligands. Pharmacological inhibition of Src kinase activity fully prevented cilengitide-induced phosphorylation of Src, FAK and VE-cadherin, and redistribution of aV beta 3 and VE-cadherin and partially prevented increased permeability, but did not prevent HUVEC detachment from low-density matrices. Taken together, these observations reveal a previously unreported effect of cilengitide on endothelial cells namely its ability to elicit signaling events disrupting VE-cadherin localization at cellular contacts and to increase endothelial monolayer permeability. These effects are potentially relevant to the clinical use of cilengitide as anticancer agent.